#define _CRT_SECURE_NO_WARNINGS 1

#include <stdio.h>

int main()
{
	int count = 0;
	int n = 10;
	for (int i = 1; i < n - 1; i++)
	{
		for (int j = n; j >= i; j--)
			count++;
	}
	printf("%d\n", count);
	return 0;
}